Improved cognitive functioning in obese adolescents after a 30-week inpatient weight loss program.

INTRODUCTION: Studies linked obesity with a large number of medical conditions including decreased cognitive functioning. The relation between BMI and cognition was proven in adults, but in adolescents the results are conflicting. Further, limited data are available on the impact of weight loss on cognition. This study analyzed the impact of a 30-week lasting weight loss program on cognition and determined the impact of changes in body composition and self-perceived fatigue on changes in cognition. METHODS: Sixty-two obese adolescents were evaluated at baseline and after 30 weeks. Stroop test (ST; selective attention), Continuous Performance Test (CPT; sustained attention) and Ray Auditory verbal learning test (RAVLT; short-term memory) were assessed. Additionally, body composition parameters and fatigue (MFI-20) were evaluated. RESULTS: Improved reaction times were found for ST and CPT after the intervention, but were independent for reductions in BMI, fat mass, fat%, and fatigue. Short memory also improved with decreased fatigue as an influencing parameter. Accuracy of ST and CPT showed no significant changes. CONCLUSION: A 30-week lasting inpatient weight loss program improved selective attention, sustained attention, and short-term memory. Changes in body composition did not explain the improvements in cognitive functioning. Decreased fatigue resulted in improved aspects of cognition.

Reaction time in healthy elderly is associated with chronic low-grade inflammation and advanced glycation end product.

Chronic inflammation and Advanced Glycation End products (AGE) are associated with sarcopenia. Decreased voluntary muscle activation and increased antagonist coactivation can contribute to age-related muscle weakness. The influence of chronic inflammation and AGE in these neuromuscular mechanisms is not clear. We studied whether a relation exists between circulating levels of inflammatory cytokines and AGEs as well as the interplay between agonist and antagonist muscle activation. We studied 64 community-dwelling old subjects, during a maximal isometric voluntary contraction (MVC) and a reaction-time (RT) test of the upper limb. Twenty-five circulating inflammatory biomarkers were determined. Linear regression showed significant relationships between chronic inflammation and six muscle activation parameters. MIP-1ß showed a significant negative relation with antagonist coactivation (during MVC) and antagonist muscle activity during pre-movement time (PMT) and movement time (MT) (during RT). A higher level of pentosidine (AGE) was predictive for a longer PMT. We conclude that in older relatively healthy persons antagonist muscle activation is influenced by chronic inflammation, contributing to age-related muscle weakness. Our results also suggest a mechanical and inflammatory influence of pentosidine in upper limb slowing of movement. These findings show novel insight in underlying mechanisms of age-related muscle weakness.

Self-perceived fatigue in adolescents in relation to body composition and physical outcomes.

BackgroundIncreased self-perceived fatigue (SpF) has already been identified in chronic conditions such as obesity, but it is also a growing problem in school-attending adolescents (±25%). This study tried to link body composition to SpF and physical activity/performance. Additionally, indicators for fatigue were determined.MethodsA total of 452 adolescents were recruited. Body composition was measured and physical activity, physical performance, and SpF were assessed. Based on the total SpF (Multidimensional Fatigue Inventory) outcomes, three groups were created: low fatigue (LF) medium fatigue (MF) and high fatigue (HF).ResultsFat was significantly lower in the LF group compared with MF (P<0,05) and HF (P<0.01). Grip endurance was increased in LF (P<0.05) and MF (P<0.01) compared with HF; similar results were found with the Cooper test. Sport Index was increased in LF compared with MF and HF (P<0.01). Fat and physical activity were related to fatigue (P<0.01). Decreased fatigue resistance, Sport Index and higher fat percentage increased the chance of being extremely fatigued.ConclusionThis study emphasizes the importance of using fat mass and fat percentage instead of body mass index when screening adolescents. To prevent increased SpF, it is necessary to stimulate youngsters to be physically active and to promote healthy behaviors.

Peripheral muscle fatigue in hospitalised geriatric patients is associated with circulating markers of inflammation.

Geriatric patients with acute infection show increased muscle weakness and fatigability but the relative contribution of central and peripheral factors is unclear. Hospitalised patients with acute infection (82±6years, N=10) and community-dwelling controls (76±6years, N=19) sustained a maximal voluntary isometric contraction of the M. Adductor Pollicis until strength dropped to 50% of its maximal value. Voluntary muscle activation (VA) was assessed before and at the end of the fatigue protocol using twitch interpolation method and muscle activity was monitored using surface electromyography. Twenty-five circulating inflammatory biomarkers were determined. At pre-fatigue, no significant difference in VA was found between groups. VA decreased to similar levels (~50%) at the end of the fatigue protocol with no association with inflammatory biomarkers. In geriatric patients, muscle activity decreased significantly (p<0.05) during the fatigue protocol, whereas it increased in the controls (time∗group interaction p<0.05). The decrease in muscle activity was significantly related to higher levels of inflammation. Although slower muscle contraction and relaxation were significantly related to higher levels of inflammation, no statistical differences were found between groups. Our results confirm that muscle activity is significantly altered in older patients with acute infection and that local processes are involved.

Predicting appendicular lean and fat mass with bioelectrical impedance analysis in older adults with physical function decline - The PROVIDE study.

BACKGROUND & AIMS: No generalizable formulas exist that are derived from bioelectrical impedance analysis (BIA) for predicting appendicular lean mass (ALM) and fat mass (AFM) in sarcopenic older adults. Since precision of regional body composition (BC) data in multicentre trials is essential, this study aimed to: 1) develop and cross-validate soft tissue BIA equations with GE Lunar and Hologic DXA systems as their reference 2) to compare our new ALM equation to two previously published models and 3) to assess the agreement between BIA- and DXA-derived soft tissue ratios as indicators of limb tissue quality. METHODS: Two-hundred and ninety-one participants with functional limitations (SPPB-score 4-9; sarcopenia class I or II, measured by BIA) were recruited from 18 study centres in six European countries. BIA equations, using DXA-derived ALM and AFM as the dependent variable, and age, gender, weight, impedance index and reactance as independent variables, were developed using a stepwise multiple linear regression approach. RESULTS: Cross-validation gave rise to 4 equations using the whole sample: ALMLUNAR (kg) = 1.821 + (0.168*height2/resistance) + (0.132*weight) + (0.017*reactance) - (1.931*sex) [R2 = 0.86 and SEE = 1.37 kg] AFMLUNAR (kg) = -6.553 - (0.093* height2/resistance) + (0.272*weight) + (4.295*sex) [R2 = 0.70 and SEE = 1.53 kg] ALMHOLOGIC (kg) = 4.957 + (0.196* height2/resistance) + (0.060*weight) - (2.554*sex) [R2 = 0.90 and SEE = 1.28 kg] AFMHOLOGIC (kg) = -4.716 - (0.142* height2/resistance) + (0.316*weight) + (4.453*sex) - (0.040*reactance) [R2 = 0.73 and SEE = 1.54 kg] Both previously published models significantly overestimated ALM in our sample with biases of -0.36 kg to -1.05 kg. For the ratio of ALM to AFM, a strong correlation (r = 0.82, P < 0.0001) was found between the mean estimate from BIA and the DXA models without significant difference (estimated bias of 0.02 and 95% LOA -0.62, 0.65). CONCLUSION: We propose new BIA equations allowing the estimation of appendicular lean and fat mass. Our equations allow to accurately estimate the appendicular lean/fat ratio which might provide information regarding limb tissue quality, in clinical settings. Furthermore, these BIA equations can be applied to characterize sarcopenia with Hologic and Lunar reference values for BC. Previously published BIA-based models tend to overestimate ALM in sarcopenic older adults. Users of both GE Lunar and Hologic may now benefit from these equations in field research.

Age-related differences in muscle recruitment and reaction-time performance.

Previously, we showed that prolonged reaction-time (RT) in older persons is related to increased antagonist muscle co-activation, occurring already before movement onset. Here, we studied whether a difference in temporal agonist and antagonist muscle activation exists between young and older persons during an RT-test. We studied Mm. Biceps (antagonist muscle) & Triceps (agonist muscle) Brachii activation time by sEMG in 60 young (26 ± 3 years) and 64 older (80 ± 6 years) community-dwelling subjects during a simple point-to-point RT-test (moving a finger using standardized elbow-extension from one pushbutton to another following a visual stimulus). RT was divided in pre-movement-time (PMT, time for stimulus processing) and movement-time (MT, time for motor response completion). Muscle activation time 1) following stimulus onset (PMAT) and 2) before movement onset (MAT) was calculated. PMAT for both muscles was significantly longer for the older subjects compared to the young (258 ± 53 ms versus 224 ± 37 ms, p=0.042 for Biceps and 280 ± 70 ms versus 218 ± 43 ms for Triceps, p<0.01). Longer agonist muscle PMAT was significantly related to worse PMT and RT in young (respectively r=0.76 & r=0.68, p<0.001) and elderly (respectively r=0.42 & r=0.40, p=0.001). In the older subjects we also found that the antagonist muscle activated significantly earlier than the agonist muscle (-22 ± 55 ms, p=0.003). We conclude that in older persons, besides the previously reported increased antagonist muscle co-activation, the muscle firing sequence is also profoundly altered. This is characterized by a delayed muscle activation following stimulus onset, and a significantly earlier recruitment of the antagonist muscle before movement onset.

Age-related differences in pre-movement antagonist muscle co-activation and reaction-time performance.

Multiple causes contribute to the prolonged reaction-times (RT) observed in elderly persons. The involvement of antagonist muscle co-activation remains unclear. Here the Mm. Biceps and Triceps Brachii activation in 64 apparently healthy elderly (80 ± 6 years) and 60 young (26 ± 3 years) subjects were studied during a simple RT-test (moving a finger using standardized elbow-extension from one pushbutton to another following a visual stimulus). RT was divided in pre-movement-time (PMT, time for stimulus processing) and movement-time (MT, time for motor response completion). RT-performance was significantly worse in elderly compared to young; the slowing was more pronounced for MT than PMT (respectively 101 ± 10 ms and 41 ± 6 ms slower, p<0.01). Elderly subjects showed significantly higher (p<0.01) antagonist muscle co-activation during the PMT-phase, which was significantly related to worse MT and RT (p<0.01). During the MT-phase, antagonist muscle co-activation was similar for both groups. It can be concluded that increased antagonist muscle co-activation in elderly persons occurs in an early phase, already before the start of the movement. These findings provide further understanding of the underlying mechanisms of age-related slowing of human motor performance.